Dental Abscesses for Medical Students
Dentoalveolar infection is a common dental emergency that will present not only to the dentist but will often be seen at GP surgeries, A&E departments and on the wards. The term refers to pyogenic conditions that affect the teeth and supporting structures, by far the most common of which is the acute periapical abscess (acute dentoalveolar abscess).
Acute Periapical Abscess
An acute periapical abscess is a collection of pus at the apex of a tooth with dead pulp. The pulp (the tooth's nerve and blood supply) may become necrotic in a number of ways. Usually it is secondary to invasion of the pulp by bacteria after a cavity is formed in the tooth by dental caries (decay) although it can also occur following trauma to the tooth.
The classical feature of an acute dental abscess is severe dental pain. It is often poorly localised by the patient and may keep them awake at night. On examination the affected tooth frequently has a carious cavity, is discoloured, tender to percussion and may respond negatively to sensitivity tests, such as touching the tooth with a cotton wool pledget covered with ethyl chloride. As the abscess progresses, the infection spreads through the alveolar bone surrounding the tooth and into the soft tissues. This is associated with a decrease in the pain felt by the patient and a soft, fluctuant swelling which may be detectable clinically in the oral cavity.
Diagnosis and Investigation
Diagnosis is largely clinical from the history and examination but dental radiographs can provide confirmation. Dentists will take intra-oral periapical radiographs and although orthopantomogram (OPG) radiographs are commonly used in hospitals, they are not as accurate in diagnosing dental caries and infection. Radiographic signs vary greatly in dental abscesses from a marked, well defined periapical radiolucency to a subtle widening of the periapical lamina dura.
Microscopy, culture and sensitivity of aspirated or incised dental abscesses can be helpful in directing antimicrobial therapy but it is rarely done in simple abscesses as it can take up to 48 hours to obtain the results. It is more commonly undertaken in severe cases requiring hospitilization (see later) or where initial treatment has been unsuccessful.
As with all abscesses, the guiding treatment principle is to remove the pus. In the acute setting this can be achieved by:
- The root canal - the dentist can open up the crown of the tooth to expose the pulp network and allow drainage.
- The tooth socket - following extraction of the tooth.
- Incision and drainage of any fluctuant intra-oral swelling
Although all of the above are treatment options, incision and drainage and antibiotics only deal with the acute infection and not the source meaning that recurrance is likely. Following the acute management, the tooth must be treated. This involves either a root canal treatment to clean out and fill the pulp canals or tooth extraction depending on the viability of tooth restoration and the patient's wishes.
Dentoalveolar abscesses are usually polymicrobial and anaerobic in nature. Common organisms isolated are anaerobic streptococci, Actinomyces, Prevotella and Porphyromonas spp. In recent years, concern has grown over bacterial resistance and so antibiotic therapy must be chosen with care and should be limited to patients who are systemically unwell or where adequate surgical drainage is not possible. Despite resistance, amoxicillin or penicillin V remain first line with metronidazole or erythromycin the treatment of choice in those with penicillin allergies.
If dental abscesses are not adequately treated, they can progress and infection can spread through tissue spaces beyond the oral cavity. At this point, patients can become systemically unwell and referral to a hospital specialist is required. Signs of systemic infection include tachycardia, pyrexia, hypotension, tachypnoea and difficulty in breathing or swallowing.
The route of spread is influenced by the position of the roots of the tooth involved and the anatomy of the surrounding area. Some possible tissue spaces include:
- Buccal - in the cheek lateral to the buccinator muscle
- Submandibular - below the angle of the mandible
- Sublingual - underneath the tongue
- Submental - below the chin
- Parapharyngeal - lateral to the pharynx in the posterior oral cavity
A medical emergency due to infection spreading across the floor of mouth to threaten the airway. The term "angina" literally means strangling or choking and describes what the patient feels. Infection is usually of odontogentic origin and starts in the submandibular space before spreading to the sublingual and submental spaces on both sides. Ludwig's Angina requires prompt treatment with airway management, such as intubation or tracheostomy, surgical drainage and antibiotic therapy.
Cavernous Sinus Thrombosis:
Rarely, spreading facial cellulitis can infiltrate the cavernous sinus via the facial vein. This can cause life-threatening intracranial infection.